Honestly, I've been running Chris's Highframes config for about a month now and I WAS (repeat, WAS) very happy about it. My frames were between 100 and 120, the game was so smooth and I enjoyed it very much.
Lately though the framerate dropped to 30-40 frames per second, which is very unpleasant. I've been trying to fix it, even loading the defaults with DX 9, but nothing seemed to help.

Is there anyhing possible to fix it (either by someone or by Valve themselves), so I can play normally again? It's frustrating...

Honestly, I've been running Chris's Highframes config for about a month now and I WAS (repeat, WAS) very happy about it. My frames were between 100 and 120, the game was so smooth and I enjoyed it very much.
Lately though the framerate dropped to 30-40 frames per second, which is very unpleasant. I've been trying to fix it, even loading the defaults with DX 9, but nothing seemed to help.

Is there anyhing possible to fix it (either by someone or by Valve themselves), so I can play normally again? It's frustrating...

Jake is your performance decrease since the latest update? That's when I started noticing issues identical to yours. I am in work atm so can't try this thread, but it will be first thing I do when I walk through the door tonight. Shall I assume it did nothing for you though? :/

Well, yes. I had a short break from Friday till Monday, that's when all this started happening. 60FPS loss is just ridiculous.
Tried to do everything, but turning on the DirectX 9 is not helping at all. If you can aid me and people around somehow, I'd be very grateful.

No idea if this indicates anything... I also have a 120GB SSD which is super fast but also nearly full. Is it possible something is clogging up my SSD is it tries to run the graphics files or even that its nearly full causing frame stutter?

I used to play on my computer with much smaller screen (1200x1100something), with almost all settings set to the max, getting about 60FPS. As I bought the larger screen, had to sacrifice the graphics for performance, getting 100-120FPS in fights. Latest update broke that.
Using the highframes script by chris with all the ragdolls and facial flexes on.

I run no antivirus while playing TF2. I only use Windows Defender anyway
HDD is fully defrag'd and everything
I have solid 90Mbps download/ 60Mbps upload connection, no lag spikes.

No matter what settings I use my fps is just around the same (even with chris fps configs, maxquality and dx9frames-highframes are pretty much the same). Never really gets over 120-130 and drops often to 40-50 for short periods, it feels really jittery.

Windows Defender / MS Essentials are the crappiest and is nothing then a bad patchup for a antivirus/antispyware. Get a real anti-virus / anti-spyware for that.

Ehm, with the C2D thats a dual core, so that 50% is just 1 core being topped to the max probably. Shame the "multicore rendering" on dual cores isn't really paying off. I'd try running singlecore (if its set on multicore, if not try vv)

I have to run tf in dx8 with chris's max frames config to keep from random framerate drops, but I finally got it up and running on linux, and it runs even better than it does in windows 7. It still suffers from random frame drops from time to time, but it is not related to things such as pyro setting a bunch of stuff on fire, but rather to not-so-perfect optimization on linux at this point. I even used the max quality config and never dropped below 60fps on linux when playing mvm and there were crit rockets and such flying everywhere. Normally I get frame drops on windows 7 in dx8 under the same circumstances. Whatever optimizations valve may have implemented from the linux version, I hope they can get them working in windows, as considering tf2 was built natively for windows, it should run just as good if not better than the linux version. Once valve works out the kinks with frame stability in linux though, I might make the full switch.

I am currently playing with Chris´ Highframes config and it have worked well since Halloween but now I am noticing very annoying issue.
During setup time, standing still etc. fps is nearly 200. But when getting to the action it drops immediately to about 50-60.
Not that 50-60 fps itself annoys me but that constant jumping between fps values messes my hitscan aim drastically.

edit: I play with 1366x768 with settings medium to low.

So is there any way to like "lock"/ stabilize the fps so the difference between max and min won´t be so high.